V.8 : Procedures for starting sessions of data transmission over the public switched telephone network

V.8 bis : Procedures for the identification and selection of common modes of operation between data circuit-terminating equipments (DCEs) and between data terminal equipments (DTEs) over the public switched telephone network and on leased point-to-point telephone-type circuits

V.21 : 300 bits per second duplex modem standardized for use in the general switched telephone network

V.22 : 1200 bits per second duplex modem standardized for use in the general switched telephone network and on point-to-point 2-wire leased telephone-type circuits

V.22 bis : 2400 bits per second duplex modem using the frequency division technique standardized for use on the general switched telephone network and on point-to-point 2-wire leased telephone-type circuits

V.23 : 600/1200-baud modem standardized for use in the general switched telephone network

V.25 : Automatic answering equipment and general procedures for automatic calling equipment on the general switched telephone network including procedures for disabling of echo control devices for both manually and automatically established calls

V.26 : 2400 bits per second modem standardized for use on 4-wire leased telephone-type circuits

V.26 bis : 2400/1200 bits per second modem standardized for use in the general switched telephone network

V.26 ter : 2400 bits per second duplex modem using the echo cancellation technique standardized for use on the general switched telephone network and on point-to-point 2-wire leased telephone-type circuits

V.27 : 4800 bits per second modem with manual equalizer standardized for use on leased telephone-type circuits

V.27 bis : 4800/2400 bits per second modem with automatic equalizer standardized for use on leased telephone-type circuits

V.27 ter : 4800/2400 bits per second modem standardized for use in the general switched telephone network

V.61 : A simultaneous voice plus data modem, operating at a voice plus data signalling rate of 4800 bit/s, with optional automatic switching to data-only signalling rates of up to 14 400 bit/s, for use on the General Switched Telephone Network and on leased point-to-point 2-wire telephone type circuits

V.70 : Procedures for the simultaneous transmission of data and digitally encoded voice signals over the GSTN, or over 2-wire leased point-to-point telephone type circuits